Honda CX 500 Forum banner

21 - 40 of 49 Posts

·
Registered
1983 cx650E
Joined
·
849 Posts
When reusing rubber o-rings or parts diaphragms etc steer clear of WD-40 and similar penetrating oils as they expand and swell the rubber. The last time I did a did a brake master cylinder and caliper rebuild, I used brake cleaner to clean and petroleum jelly or Vaseline to freshen the rubber. And I reused a fuel pump diaphragm on a 19 horse Briggs & Stratton using Vaseline. I couldn't get the new rubber to work then I pinched it so I went back to the old rubber lubed it up and it worked first time. Just a thought, unless someone has objections to using vaseline.
 

·
Registered
1983 cx650E
Joined
·
849 Posts
I wouldn't rule out the fuel petcock diaphragm either but I think it's more likely the carb issues. You could rule out the fuel petcock diaphragm by running a gasoline hanger bottle directly to the carbs. If a fuel petcock diaphragm is perforated and just the right way it would allow just a certain amount of fuel to fill the bowls when you're accelerator uses up that fuel it would shut down until more fuel was put into the bowls. More likely your carb issues but who knows?
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #24
I wouldn't rule out the fuel petcock diaphragm either but I think it's more likely the carb issues. You could rule out the fuel petcock diaphragm by running a gasoline hanger bottle directly to the carbs. If a fuel petcock diaphragm is perforated and just the right way it would allow just a certain amount of fuel to fill the bowls when you're accelerator uses up that fuel it would shut down until more fuel was put into the bowls. More likely your carb issues but who knows?
There's an inline fuel filter that I can verify has fuel in it, would that be enough to eliminate this?

Now the way it's run the lines are kinked a tiny bit so I could try and straighten that out too but it was this way with the previous owner too.

Really it's all just speculation until I get the carbs rebuilt, so just ordered the cheap kit ($12 US for 2 carbs) as a starting point. The Randakks one is $85-$105 + $42 US shipping to Canada and the bike only cost me $390 US! I get there's cost in restoring a vintage bike but I don't want to go all-out on each part just yet. :D
 

·
Registered
1983 cx650E
Joined
·
849 Posts
I would think that if the fuel filter retains fuel while it's stumbling that that should rule out the fuel petcock as a problem. Even on that 19 horsepower Briggs that I mentioned using vaseline on the diaphragm, I could tell that the diaphragm wasn't working because there was no fuel flowing through the fuel filter. When the diaphragm was sealed right and pulsating right then the fuel started to flow and would shut off when the fuel bowl was filled and the float had seated the needle valve

I almost always bring up the fuel petcock valve as a possibility because one time I had a gl500 that would starve itself of fuel on the road then start back up etc. After cleaning the carbs twice swapping coils installing new igniters and probably other things I sold it to another fellow more mechanically inclined than I, who basically repeated what I did. He ended up selling it to another fellow in his neighborhood who found the culprit problem of a perforated diaphragm in the petcock valve. It was a pretty nice gl500 that I probably would have kept if not for the poor running issues.

Well, got to g for now,, take care and good luck.
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #27
Thanks @TonyG! I will give the petcock a second look just to be sure, I don’t know if it’s the original or not as it’s definitely not hooked up in vacuum mode anymore as the vacuum port on the right carb is capped off currently. I’ll give it a check though, thanks!
 

·
Premium Member
1978 CX500, 1982 GL500 Silverwing Interstate, 1980 CX500 Custom
Joined
·
49 Posts
I am probably way off base here, but if you have the carbs off anyway - why not do a compression check on each cylinder. I think you mentioned possibly replacing the Valve Cover gasket due to over tightening. Maybe there's more to it on that cylinder?

The compression/leak test will reveal condition on valves, piston rings, or maybe head gasket. If the oil was nice an black when you drained it, then it probably won't be a head gasket leaking coolant into the oil channels.

But bad valves/rings could mean oil is accumulating and or getting burned, and if only running for very short periods could just pool in the collector.

Even if this isn't the cause - doing the test will give you some peace of mind about the state of each cylinder. If memory serves, compression with a wide open throttle should be above 150 - 190 psi, with both cylinders in a close range to each other.

Good luck, looks like it has the potential to be a nice bike!
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #29 (Edited)
I am probably way off base here, but if you have the carbs off anyway - why not do a compression check on each cylinder. I think you mentioned possibly replacing the Valve Cover gasket due to over tightening. Maybe there's more to it on that cylinder?

The compression/leak test will reveal condition on valves, piston rings, or maybe head gasket. If the oil was nice an black when you drained it, then it probably won't be a head gasket leaking coolant into the oil channels.

But bad valves/rings could mean oil is accumulating and or getting burned, and if only running for very short periods could just pool in the collector.

Even if this isn't the cause - doing the test will give you some peace of mind about the state of each cylinder. If memory serves, compression with a wide open throttle should be above 150 - 190 psi, with both cylinders in a close range to each other.

Good luck, looks like it has the potential to be a nice bike!
Tracked down a compression gauge from a buddy, so I'll give that a check along with all of the other non-engine-removing things I can think of. I have no idea why the left valve cover was off in the first place to get stripped/resealed so checking the compression is a great suggestion, thank you!

If compression is fine on both sides I'll probably just leave them in place for the time being, but if I need to check the valves or anything I'll pick up at least one gasket kit as the left one already looks like it was sealed up a bit with liquid gasket and won't likely survive another opening.
 

·
Super Moderator
Joined
·
15,165 Posts
FWIW, similar problems have been traced to inline fuel filters that don't have the outlet lower than the inlet so when more fuel is needed as the revs increase it can't get to the outlet fast enough.

But if I found the insides of the carbs looking like that I'd want to clean them thoroughly before I started looking elsewhere too.
And if there was fuel in the tank I'd be thinking about ways to clean that and the petcock too.

BTW: Welcome to the forum and welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and the Previous Owners may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet). If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for mode
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #31 (Edited)
So I thought I had sorted out the left cylinder firing, but it seems like I'm still only getting the right one, pull the plug cap on the left no change, pull the one on the right and it dies. It seems to have spark and I've swapped the ignitors and it's the same so still could be fuel getting to the carb, if I spray carb cleaner into the left carb I get a nice rev boost so I think that's a sign towards fuel flow in the left carb is it not? Sprayed into the right and it stalls too, probably too rich.

I'd like to re-route this fuel line sometime to get it out of the way a bit and take out the kink, on the to-do list especially with comments around flow but I think we're still in carb-town here! Also doesn't appear to be original petcock as there's no vacuum or vent hose.

IMG_2789.jpeg
 

·
Super Moderator
Joined
·
15,165 Posts
That sounds like a plugged jet or passage.

Replacing the original vacuum petcock with a non-vacuum one is a pretty common solution to the hard starting problem associated with vacuum ones (fuel evaporates from the bowls and after a few days there isn't enough left for starting so you have to crank the engine fast enough to produce sufficient vacuum to open the petcock's vacuum valve long enough to let the bowls re fill before it can start). It should be fine as long as the barb for the vacuum line (usually on the left side of the right carb's outlet) is capped.

Some people recommend adding an inline fuel filter to prevent rust/debris from the tank from getting into the carbs but that is only a band aid fix; The proper solution is to make sure the tank is clean and have it epoxy lined if it is rusty.
As I said before, if I found stuff like that inside the carbs I'd want to look inside the petcock & tank too. The first thing to do is remove the petcock and look for dirt in the filter that is supposed to be inside the tank over the petcock's inlets. If it looks clean you probably don't need the external filter.
 

·
Super Moderator
Joined
·
4,185 Posts
.... if I spray carb cleaner into the left carb I get a nice rev boost so I think that's a sign towards fuel flow in the left carb is it not? Sprayed into the right and it stalls too, probably too rich.
The carb spray in the left carb resulting in a rev boost shows that you have a good spark on the left cylinder and lack of fuel.
 
  • Like
Reactions: Unsta

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #34
That sounds like a plugged jet or passage.

Replacing the original vacuum petcock with a non-vacuum one is a pretty common solution to the hard starting problem associated with vacuum ones (fuel evaporates from the bowls and after a few days there isn't enough left for starting so you have to crank the engine fast enough to produce sufficient vacuum to open the petcock's vacuum valve long enough to let the bowls re fill before it can start). It should be fine as long as the barb for the vacuum line (usually on the left side of the right carb's outlet) is capped.

Some people recommend adding an inline fuel filter to prevent rust/debris from the tank from getting into the carbs but that is only a band aid fix; The proper solution is to make sure the tank is clean and have it epoxy lined if it is rusty.
As I said before, if I found stuff like that inside the carbs I'd want to look inside the petcock & tank too. The first thing to do is remove the petcock and look for dirt in the filter that is supposed to be inside the tank over the petcock's inlets. If it looks clean you probably don't need the external filter.
I'll put those things on the list! Gas in the inline filter has looked clean, and I can't go by the old filter as everything went gross in there likely from sitting. Inside of the tank is pretty rusty as when it was left for 2 years it only had about 1/6 tank of gas in it, but I can check the petcock filter too, shouldn't be much work to drain the tank again, just have to listen to my wife complain about me smelling like gas again!

Vacuum line on the right carb is definitely capped off (with a screw in the hose - probably do something a little nicer looking)
 

·
Registered
Joined
·
5 Posts
Bought a CX500C from a former co-op student of mine, someone had started to cafe it up a bit before him and he did some work as well. Odometer reads 26k or so (miles) so no idea if that's 26 or 126.

Sat for 2 years and he was moving so was selling, "ran fine" before sitting so currently working on air/fuel/spark as step one.

Wouldn't start when I got it, so replaced the battery, and took out the carbs and cleaned out the lower bowl side entirely, removed the 2 main jets and the "easy" emulsion tube, cleaned tons of green powder out of the right carb (likely 89 octane fuel with 10% ethanol that sat) and lots of gelled gas out of the left.

Got it to start up and it was only running on the right cylinder because of a poor connection from the spark cap to the wire, snugged that up and running on 2 cylinders now but stalls out at 4k-5k rpm. I haven't done the top end of the carb yet but I'm going to order 2 full rebuild kits and just do that as I didn't get to the diaphragm or the pilot jet at all, just the bottom side. It was previously converted to pods as well 2 owners ago so I need to check the main jet sizes as well although presumably it was re-jetted after the pod conversion. Float sticks on the right side (the green one) as well sometimes and needs a whack even after the cleaning so I'll need to tap that pin out and clean I think.

One thing I was hoping to get a question answered on is I'm getting black oil dripping out from the muffler connection on the kickstand side, and I don't know if it's oil making it through valve seals or something similar or if it's just residue in the exhaust. Oil is fairly clean (although will be changed this week) and the oil dripping out is very black but that might just be what happens as it makes it through the combustion chamber if it is sneaking past. The valve cover was previously overtorqued and repaired on the left side and there's gasket seal visible so I'll order some cover gaskets before I open it up, but was wondering if this is a symptom of valve stem seals / guides or if it's likely just residue.

New plugs installed as well, old plugs were quite black so maybe rich OR getting oil, not sure as they were black on both sides, have resistor plug caps so replaced with DE8A plugs.

Any help/tips greatly appreciated! It'll probably be next winter before I get brave enough for any of the big stuff (engine removal, etc) so for now looking at engine-in style things to check.
Oil leak could be the shifter seal...easy fix.
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #36 (Edited)
Oil leak could be the shifter seal...easy fix.
Oh when I picked it up there was a small bit of oil on the floor from the shifter seal for sure, that’ll get replaced but I’m no longer thinking it’s oil in the exhaust but condensation mixed with carbon in the exhaust since it’s quite cool here and upon further inspection it seems more like water mixed with sediment than oil.

Can you get those seals right from a Honda power sports dealer, or just easier to get online?
 

·
Registered
Joined
·
6,967 Posts
Oh when I picked it up there was a small bit of oil on the floor from the shifter seal for sure, that’ll get replaced but I’m no longer thinking it’s oil in the exhaust but condensation mixed with carbon in the exhaust since it’s quite cool.

Can you get those seals right from a Honda power sports dealer, or just easier to get online?
Honda dealer here has to order most of my parts, but I dont pay shipping
 

·
Registered
1983 cx650E
Joined
·
849 Posts
Oh when I picked it up there was a small bit of oil on the floor from the shifter seal for sure, that’ll get replaced but I’m no longer thinking it’s oil in the exhaust but condensation mixed with carbon in the exhaust since it’s quite cool.

Can you get those seals right from a Honda power sports dealer, or just easier to get online?
Deleted comments about a 10% discount from an American Honda powersports seller. I noticed that you're from Canada and the shipping duty cancels and destroys any benefit of any discount in less it would be a large order {period}
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #39 (Edited)
Honda dealer here has to order most of my parts, but I dont pay shipping
Which is why I'd happily order it at the dealer! Plus being in Canada places in the US that offer "Free US Shipping" usually translates to $5-10 (if you're lucky) or $50-180 for shipping to Canada because they use DHL or something else that's crazy expensive, or they just want to gouge.

UPDATE: Called the dealer - $6.50 CDN, no shipping. Not quite as good as the $2.53US on the discount honda parts site, but I'll take it!
 

·
Registered
1982 CX500C (US)
Joined
·
20 Posts
Discussion Starter #40
Tracked down a compression gauge from a buddy, so I'll give that a check along with all of the other non-engine-removing things I can think of. I have no idea why the left valve cover was off in the first place to get stripped/resealed so checking the compression is a great suggestion, thank you!

If compression is fine on both sides I'll probably just leave them in place for the time being, but if I need to check the valves or anything I'll pick up at least one gasket kit as the left one already looks like it was sealed up a bit with liquid gasket and won't likely survive another opening.
Friend's compression gauge was for oil and transmission pressure, but it turns out NAPA has one you can "rent" for free, basically a refundable deposit under a tool loan program so I'll be doing that, hoping they have a carb sync tool as well in the same inventory.
 
21 - 40 of 49 Posts
Top